Removing airborne particles from living and working environments has traditionally been done by filters that rely on a combination of inertial impaction onto, interception with, and diffusion to the filer media's surfaces. The use of all three mechanisms enables efficient filtration over the widest possible range of particle sizes, but at the cost of large collection areas or large pressure drops. Most bacteria and molds are found in supermicrometer sizes that can be removed by inertia alone.